I am in my second semester A/P and more than 50% of my class this semester and last semester are/were taking the class for the second or third time (one girl is on her fourth round of A/P 1. For many it is not an easily grasped subject, for some the idea that it is difficult makes it harder to be successful, and for others, it's just not within them to put forth the effort. I think you are making the right choice to try again with another professor. In the meantime, go online to coursera and take a free short term physiology class and see if you can get some of the terminology down. Or maybe try taking the anatomy portion first. The physiology is easier understood if you have a good foundation of the anatomy.